Electromagnet



8 1946- c. E. BAZLEY 2,4053% ELECTROMAGNET Filed NOV. 29, 1944 llmii h I lie ' Inventbr': Carl E. Bazley,

His Attorney.

Patented Aug. 6, 1946 ELECTROMAGNET Carl E. Bazley, Schenectady, N. Y., assignor to General Electric Company, a, corporation of New York Application November 29, 1944, Serial No. 565,599

Claims. 1

My invention relates to electromagnets, more particularly to direct current electromagnets, and has for its object a simple and reliable means for preventing movement of the armature to its unattracted position in the event of a severe shock.

In a direct current magnet, if the armature is moved away from the pole face on which it is seated in its attracted position, a sharp decrease in the magnetic pull on the armature results. Such movement of the armature away from its attracted position with the coil energized may be caused by a severe shock, with rebound of the armature away from the stationary pole face in a manner somewhat similar to the so-called billiard ball effect. The great decrease in magnetic pull caused by the separation of the armature from its stationary pole face would, in most cases, result in the movement of the armature to its full unattracted position with operation of the devices connected to the armature, although it will be understood that the armature would thereafter be picked up to its attracted position if the pickup section of the coil were again energized.

In accordance with my invention, I provide means for preventing the sharp decrease in magnetic pull on the armature in the event that it is thrown away from the stationary pole face by a severe shock. In one form of my invention, I provide an auxiliary intermediate movable pole piece having a portion in telescoping relation with the stationary magnet core so that this intermediate portion can move with the armature against a spring bias in the event of a severe shock while maintaining the magnetic pull on the armature.

For a more complete understanding of my invention, reference should be had to the accompanying drawing, the single figure of which is an elevation View partly in section of an electromagnetically operated switch embodying my invention.

Referring to the drawing, in one form of my invention I provide a magnet coil 1 mounted on a suitable spool 2 made of electrically insulating material and enclosed in a cylindrical member 3 made of magnetic material which forms a part of a magnetic core for the coil. As shown, at its upper end the cylindrical member 3 is provided with a ring-shaped core member 4 provided with a central aperture through which extends a plunger armature 5. At its lower end the cylindrical core member 3 is spun or bent over and provided with a short tubular stationary core member 8 extending into the coil.

An intermediate auxiliary plunger core member '5 is provided which is movable axially of the coil in an upward direction from the position seen in the drawing against the downward biasing force applied by a helical tension spring 8. On its lower end, the core member I is provided with a smaller cylindrical portion 9 which extends downward loosely into a bore ii] in the tubular core member 6. The upper end of the spring 8 is secured to the lower end of this portion 9, while the lower end of the spring is secured to a suitable Washer or nut II on the outside of the core member 3. Thus, as shown, the spring may be secured to the extension 9 by means of a smaller threaded portion on the extension which fits into the upper end of the spring, while the nut 01 washer H has internal threads into which the iower end of the spring fits.

Thus the spring applies a substantial biasing force on the movable core member 1 in a downward direction so as to hold seated the shoulder formed between the upper and lower cylindrical portions on the upper end of the core member 6. When the coil I is energized, the armature 5 is pulled down until the lower end of the armature seats on the normally stationary pole face provided on the upper end of the member 1. The downward biasing force applied by the spring 8 is greater than the magnetic pull of the coil applied to the armature 5 up to the point where the plunger 5 is seated, or nearly seated, in its attracted position so that during the movement of the armature 5, together with the mechanism operated by the armature to its attraced position, the core member 'l' is held by the spring 8 in its seated position shown in the drawing.

When the lower end of the plunger 5 engages the stationary pole face on the upper end of the core member I, the magnetic pull applied to the armature increases very greatly because of the elimination of the air gap between the pole faces so that this sealed pull between the armature and the core member 7 becomes greater than the downward biasing force applied by the spring 8. Consequently, in the event of a shock applied to the support it on which the magnet is mounted and transmitted from the support to the magnet core and armature, the core member I can move upward against the biasing force of the spring 8 along with the armature 5 so that the sealed-in relation between the armature and the member 1 is not broken. Thus a severe shock applied to the core members 6 and l in an upward direction tends to throw the armature 5, assuming it is in its downward sealed attracted position, up-

ward away from the core member 1. Instead of this happening, however, the core member 7 moves with the armature, the spring 8 elongating. The cylindrical extension on the lower end of the core member I maintains substantially the same flux path for the coil when the member 'l is moved upward without substantial change in the magnetic flux in the member i so that the sealed pull between the members 5 and 'l is not appreciably reduced.

It will be understood that the sealed-in pull between the flange on the core member I seated on the upper end of the tubular core member 6 is not great and is only a fraction of the pull between the members 5 and l for the reason, as previously observed, that movement of the core member 7 upward away from the member ii does not sub stantially reduce the magnetic fiux through these two members.

The spring 3, however, applies a downward biasing force to the core member i which does not decrease when the core member I is moved upward and in fact will increase somewhat. Thus, in the event of a shock which throws the armature upward, the spring applies a force to return the armature to its attracted position which is much greater than the normal magnetic pull on the armature.

A guide tube it made of a' nonmagnetic material, such as brass, is provided in the bore of the coil so as to serve as a guide for the armature 5 and the core member i, and also as an air gap between the armature and core member 3.

A guide pin i made of a nonmagnetic material, such as phosphor bronze, has its upper end secured to the lower, end of the armature 5 and its lower end extending loosely in a central bore in the core member I. This rod i l serves as a guide for the lower end of the armature.

Although any suitable switch or mechanism can be connected to the armature 5 for operation thereby, I have shown the armature connected to an electric switch of the type described and claimed in my copending application Serial No. 551,484, filed August 28, 1944. This switch comprises a slider plate i5 made of electrically insulating material which is slidably mounted on a support it and provided with a plurality of apertures ii for controlling the engagement and separation of pairs or spring contacts l8, Thus, when the slider is in its uppermost position to which it is biased by the springs i9 and 20, a projection 2i separates the pair of contacts it while another pair of contacts lilo; are moved together by the side walls of a narrow portion of the slot.

While I have shown a particular embodiment of my invention, it will be understood of course that I do not wish to be limited thereto since many modifications may be made and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electromagnet comprising a coil, a magnet core for said coil, an armature for said magnet core, an intermediate core member mounted in abutting engagement with said magnet core between said armature and said magnet core for movement away from said magnet core in the direction of movement of said armature to its unattracted position, said armature being movable by energization of said coil to an attracted position in engagement with said intermediate core member, a magnetic connection between said intermediate core member and said magnetic core providing for movement of said intermediate core member without substantial decrease in the magnetic flux in said intermediate core member, and a Spring holding said intermediate core member in abutting engagement with said magnet core with a force substantially greater than the magnetic force efiecting movement of said armature into engagement with said intermediate core member whereby said spring yields to provide for movement of said armature in the event of a shock applied to said magnet core while the coil is energized.

2. An electromagnet comprising a coil, a magnet core for said coil, an intermediate core member movably mounted for abutting engagement with said magnet core when moved in one direction, an armature for said coil movable in said direction by energization of said coil to an attracted position in engagement with said intermediate core member, and a spring normally holding said intermediate core member in abutting engagement with said magnet core with a force substantially greater than the magnetic force eiiecting movement of said armature, said intermediate core member and said magnet core being constructed and arranged with walls rela-.- tively slidable in the direction of movement of said armature so that said intermediate core member is movable away from said magnet core against the force of said spring in response to a shock while the coil is energized without substantial decrease in the magnetic force holding said armature and said intermediate core member together whereby said intermediate core member and said armature are thereafter returned by said spring to their attracted positions.

An electromagnet comprising a coil, a magnet core for said coil having a core portion at one end of said coil, an intermediate core member in said coil movably mounted in a position in abutting engagement with said core portion, a plunger armature extending into the other end of said coil movable by energization of said coil to an attracted position in engagement with said intermediate core member, and a spring normally holding said intermediate core member in said position in abutting engagement with said core portion with a force substantially greater than the magnetic force eifecting movement of said armature, said intermediate core member and said core portion being constructed and arranged with axially extending relatively slidable walls so that said intermediate core member is movable axially against the force of said spring in response to a shock while the coil is energized without substantial decrease in the magnetic force holding said armature and said intermediate core member together whereby said intermediate core member and said armature are thereafter returned by said spring to their attracted positions.

l. An electromagnet comprising a coil, a magnet core for said coil having a portion extending into one end of said coil, an intermediate movable core member in said coil, a spring normally holding said intermediate core member in abutting engagement on one side with said core portion, and a plunger armature extending into the other end of said coil movable into engagement with the opposite side of said intermediate core member when said coil is energized, an axially extending projection on said intermediate core member, said core portion being shaped with a wall in slidable engagement with said extension axially of said coil so that said intermediate core member is movable axially without substantial change in the reluctance of the magnetic circuit through said portion and said intermediate core member, said spring applying a force to said intermediate core member which is substantially greater than the magnetic force applied to effect movement of said armature whereby said intermediate core member normally is held in engagement with said core portion by said spring when said armature is moved by said coil, said spring yielding to provide for movement of said armature and said intermediate core member together in the event of a shock when said coil is energized.

5. An electromagnet comprising a coil, a plunger armature extending into one end of said coil, a magnet frame for said coil having a portion extending into the other end of said coil provided with a bore concentric with said coil and with an annular pole face on the same side of said portion as said armature, an intermediate movable core member in said coil having on one end a flange seated on said annular pole face and a cylindrical portion fitting slidably into said bore, and a spring for biasing said intermediate core member against said annular pole face with a force substantially greater than the magnetic force applied to said armature in moving it to its attracted position but smaller than the sealed-in pull between said armature and the other end of said intermediate core member when said armature is seated in its attracted position on said intermediate core member whereby in the event of of shock said spring yields to provide for movement of said auxiliary core member with said armature.

CARL E. BAZLEY. 

